1. Field of the Invention
Embodiments of the present invention generally relate to a method and an apparatus for measuring an electroless plating solution and individual components of the electroless plating solution using Raman spectroscopy.
2. Description of the Related Art
Recent improvements in circuitry of ultra-large scale integration (ULSI) on substrates indicate that future generations of integrated circuit (IC) semiconductor devices will require smaller multi-level metallization. The multilevel interconnects that lie at the heart of this technology require planarization of interconnects formed in high aspect ratio features, including contacts, vias, lines and other features. Reliable formation of these interconnects is very important to the success of ULSI and to the continued effort to increase circuit density by decreasing the dimensions of semiconductor features and decreasing the widths of interconnects (e.g., lines) to 0.13 μm and less. Currently, copper and its alloys have become the metals of choice for sub-micron interconnect technology because copper (Cu) has a lower resistivity than aluminum (Al) (i.e., 1.67 μΩ-cm for Cu as compared to 3.1 μΩ-cm for Al), a higher current carrying capacity, and significantly higher electromigration resistance.
One method for copper deposition is metal plating. Metal plating is used in a large variety of industrial processes. Plating systems, in which an object is placed in a plating solution to apply a metallic coating to the object, are well known in the art. Metal plating is used to plate a variety of metals, such as for example, copper, zinc, nickel, and gold. Many metals are plated simply by immersion in a metal plating bath that uses a chemical reducing agent, called electroless plating.
The electroless plating solution comprises a metal solution and a reducing agent solution. The solutions are mixed together to form the electroless plating solution that is provided to the substrate that is to be plated. It is important that the individual solutions be mixed together in the proper concentration so that electroless deposition can proceed in the most efficient manner possible. Additionally, each individual solution of the electroless plating solution is comprised of a plurality of components. It is important that each individual solution have the proper concentration of individual components so that the solutions can be properly used to plate the substrate.
Therefore, there is a need in the art for a method and apparatus capable of measuring the combined concentration of components in an electroless plating solution. There is also a need in the art for a method and apparatus capable of measuring the concentration of the individual components that comprise each solution that is mixed to form the electroless plating solution.